In neurosurgery a stereotactic frame, for example a Leksell Stereotactic Instrument, is mounted to the skull of a patient to provide fixed references to the brain of the patient. The frame encircles the head of the patient and is mounted with screws to the skull of the patient. On the frame a stereotactic arc is mounted, which crosses over and above the head of the patient. A stereotactic apparatus is slidably mounted on the stereotactic arc via a support slide.
A stereotactic apparatus comprises a microdrive, which comprises an instrument holder, for insertion and withdrawal of an instrument with respect to a target area of the brain of the patient. The microdrive is mounted on top of an X-Y-table for fine adjustment of the instrument along the X and Y-axes. Adjustment of the microdrive at the stereotactic arc makes it possible to achieve parallel insertion paths.
Stereotactic surgery is used, for example, for brain mapping using microelectrodes, brain biopsies, DBS implantation and lesioning.
From U.S. Pat. No. 5,817,106, Real, a stereotactic guide apparatus for use with a neurosurgical headframe is known. The stereotactic guide apparatus is mounted on a slide, which is movable along a stereotactic arc. On top of the slide a platform, comprising an X-Y-table, is mounted. In the platform there is a hole for a tubular instrument guide, through which an instrument, attached to an instrument holder in connection with a microdrive, may be inserted by the microdrive.
A problem with this stereotactic guide apparatus is to be accurate in positioning of the instrument. To obtain accuracy the different parts of the X-Y-table must all have extremely small tolerances.
Another problem is the high postion of the centre of gravity, which makes the apparatus unstable.
A further problem is that the hole through the platform limits the possibility of adjustment along the X- and Y-axes.
A still further problem is that it is extremely difficult to keep the apparatus clean, which is an important factor in surgery.